1. The Field of Invention
The invention relates to a process for manufacturing and molding tracks made of elastomeric material. The invention also relates to a device for stripping out such tracks.
2. The Related Art
The use of tracks is developing in many sectors, especially that of agricultural tractors or other civil engineering machines for which the conditions of mixed rolling (both on loose ground and on roads) entail increasing quality requirements for the tracks and also reduced industrial costs.
In the text hereinbelow, the term “elastomeric material” denotes a material comprising at least one elastomer that can be reinforced with a least one reinforcing filler such as, for example, carbon black. Diene elastomers, polyurethanes and thermoplastic rubbers, inter alia, are examples of suitable elastomeric materials.
To produce a track that is circumferentially reinforced with wires or cables, provided on its outer surface with a tread design formed from components in relief intended to make progress on loose ground easier, and also provided with a series of drive blocks in relief on its inner surface to co-operate with a suitable drive means, it is possible to use, by supplying it, a process for producing a drive band formed from a reinforced rubber belt and provided on its outer surface with relief motifs.
For example, Canadian patent No. 898 672 describes a method in which, in a first stage, the belt is produced by winding on a drum formed from components, and, in a second stage, the drum bearing the belt is positioned inside a mold composed of a plurality of radially mobile sectors to mold the relief motifs on the exterior of the band. This process has the drawback of requiring a complex production of a drum, the components of which must be retractable after molding and vulcanization of the band so as to allow the band to be stripped out after molding.
Japanese document JP-09/076,369 describes a manufacturing process in which the inner drum is formed from two symmetrical cylindrical die-halves that may be moved axially relative to each other so as to strip out a track after molding and vulcanization on the drum. In the track-manufacturing position, the drum, after assembly of the die-halves, has a radially external surface on which the track is made. The laying surface is provided with a plurality of cavities for molding the drive blocks of the track. The joint plane of the cylindrical die-halves is located axially in the middle of the block molding cavities. After filling the cavities with a blend, the track reinforcement armatures are installed together with the layers of blends of suitable elastomeric materials. Finally, the track blank is covered in its non-molded and non-vulcanized form with a plurality of mold components which bear on their radially internal surface hollows prefilled with blend to mold the track tread.
This process has a certain number of drawbacks, including:                it is imperative to determine with very high precision the volumes of the blends and of the armatures, since the molding volume delimited by the outer mold and the base cylindrical drum (acting as the inner mold) very precisely regulates the volume of the track to be molded, and since the elastomer blends used are, by their nature, incompressible;        the overhang of the various outer mold components requires high-precision mechanics to avoid having areas of overthickness or areas of imperfect molding when the hollows of the outer mold are not filled before being applied against the belt; and        during the stripping of the track from the inner mold by axial separation of the two die-halves constituting the mold, the track randomly follows one or other of the die-halves, which is not convenient in an industrial environment in which such a large, heavy track needs to be manipulated, without knowing, in principle, which side of the drum to take it from in order to move it.        
There is consequently a need to develop a process for manufacturing a large-sized track, which ensures a very high quality production of the track (in particular absence of molding defects) for which the drawbacks that have just been mentioned are eliminated.